Apparatus and methods for optical neural network

A method for artificial neural network computation, the method comprising:

• receiving a first array of optical signals with an array of input waveguides;
• interfering the first array of optical signals, using an optical interference unit in optical communication with the array of input waveguides, to linearly transform the first array of optical signals into a second array of optical signals;
• guiding the second array of optical signals using an array of output waveguides, wherein at least one input waveguide in the array of input waveguides is in optical communication with each output waveguide in the array of output waveguides via the optical interference unit,
• nonlinearly transforming the second array of optical signals using a nonlinearity unit, in communication with the optical interference unit, so as to generate a third array of signals;
• and
• providing a fourth array of optical signals to the array of input waveguides based on the third array of signals.

An optical neural network, comprising:

• an array of input waveguides to receive a first array of optical signals;
• a plurality of interconnected Mach-Zehnder interferometers (MZIs), in optical communication with the array of input waveguides, to linearly transform on the first array of optical signals into a second array of optical signals via interference among the first array of optical signals, each MZI in the plurality of MZIs comprising:
• a first phase shifter configured to change a splitting ratio of the MZI;
• and
• a second phase shifter configured to shift a phase of one output of the MZI;
• an array of saturable absorbers in optical communication with the plurality of interconnected MZIs, to nonlinearly transform the second array of optical signals into a third array of optical signals, each saturable absorber in the array of saturable absorbers receiving a corresponding optical signal in the second array of optical signals;
• and
• a detector array, in optical communication with the array of saturable absorbers, to detect the third array of optical signals.